The present invention relates to an optical disk reproduction apparatus and a method for controlling an optical disk reproduction apparatus and, more particularly, to an optical disk reproduction apparatus which can successively reproduce data recorded on an optical disk and a method for controlling the optical disk reproduction apparatus.
An optical disk reproduction apparatus has a servo for controlling rotation of an optical disk and a position of an optical pickup so as to correctly read out data recorded on the disk at a constant rate. The servo is easily affected by vibrations, or flaws or dusts on the disk and thus, reading of data is sometimes interrupted. Therefore, a shockproof function is required to resume reading of data from an appropriate position so as to prevent data from being output discontinuously, even when the reading of data is interrupted. At this time, since a position where the reading of data is to be resumed cannot be decided only by the control of a position of the optical pickup, the above-described position for resumption is Usually decided after the data is confirmed by using the shockproof function.
FIG. 5 is a block diagram illustrating a structure of a prior art musical CD reproduction apparatus. A disk 21 is a CD having musical data recorded thereon. An optical pickup 22 irradiates a laser light to the disk 21 to read the musical data recorded on the disk 21. An analog signal processing unit 23 obtains conditions of tracking and focusing from the data read by the optical pickup 22 as well as binarizes the data read by the optical pickup 22. A servo 24 controls the tracking and the focusing of the optical pickup 22. A digital signal processing unit 25 comprises a CIRC (Cross-Interleave-Reed-Solomon Code) processing unit 251, a formatting circuit 252, a memory arbitration circuit 253, an output data FIFO memory 254, a comparator 255, and a buffering resumption request generating circuit 256, and processes data binarized by the analog signal processing unit 23 to output processed data as reproduced data. A memory 26 temporarily stores the data processed by the digital signal processing unit 25. A microcomputer 27 obtains information from the respective elements and controls operations of the respective elements.
An operation of the prior art musical CD reproduction apparatus will be described. The optical pickup 22 irradiates a laser light to the disk 21 and converts a light reflected from the disk 21 into a signal to output the signal to the analog signal processing unit 23. The analog signal processing unit 23 outputs conditions of tracking and focusing to the servo 24 on the basis of the signal from the optical pickup 22 as well as binarizes the signal from the optical pickup 22 to output a binarized signal to the digital signal processing unit 25. The servo 24 outputs a control signal to the optical pickup 22 on the basis of the information from the analog signal processing unit 23 to control the tracking and the focusing. The CIRC processing unit 251 performs, for the binarized data, EFM (Eight to Fourteen Modulation) demodulation, separation of CD (Compact Disk)-DA (Digital Audio) data from subcode data, and error correction processing for the CD-DA data, and outputs processed data to the formatting circuit 252. The formatting circuit 252 converts the CD-DA data output from the CIRC processing unit 251 into a prescribed format and then outputs converted data to the memory 26 via the memory arbitration circuit 253. Data buffered in the memory 26 is read out at a prescribed rate to be sent to the output data FIFO memory 254 via the memory arbitration circuit 253, and output the same as reproduced data. An amount of the data stored in the memory 26, being controlled by the. microcomputer 27, does not exceed a capacity of the memory 26.
During reproduction from the disk 21, when the microcomputer 27 detects, on the basis of the information from the servo 24, that an error occurs in the reading of data, the microcomputer 7 instructs the digital signal processing unit 25 to interrupt the buffering as well as instructs the servo 24 to move the optical pickup 22 to a position before the position of data where the reading error occurs on the disk 21. In addition, the latest block of data buffered in the memory 26 is kept in the comparator 255 as expectation data.
The comparator 255 captures the CD-DA data read out from the disk 21 after the optical pickup 22 moves, and compares the CD-DA data with the expectation data. The comparator 255 outputs xe2x80x9cHxe2x80x9d when all the data are in coincidence, and outputs xe2x80x9cLxe2x80x9d when at least one of the data is in uncoincidence, to the buffering resumption request generating circuit 256.
When the buffering resumption request generating circuit 256 receives xe2x80x9cHxe2x80x9d from the comparator 255, the buffering resumption request generating circuit 256 requests the formatting circuit 252 to resume the buffering, and then the formatting circuit 252 resumes the buffering from data following to the CD-DA data which is judged in coincidence by the comparator 255. On the other hand, when the buffering resumption request generating circuit 256 receives xe2x80x9cLxe2x80x9d from the comparator 255, the microcomputer 27 instructs the servo 24 to move the optical pickup 22 to a further forward position, and continues to compare the CD-DA data with the expectation data until the comparator 255 outputs xe2x80x9cHxe2x80x9d.
Usually, when the CD-DA data is reproduced by an optical disk reproduction apparatus having the above-described structure, the data read out from the disk 21 is controlled to be read out at a higher rate than that of data output as reproduced data from the output data FIFO memory 254. That is, a rate of buffering data in the memory 26 is higher than a rate of reading out data from the memory 26. Therefore, even when the buffering to the memory 26 is interrupted, the output data FIFO memory 254 reads out the data stored in the memory 26 at a prescribed rate and outputs reproduced data. That is, while data is stored in the memory 26, the optical disk reproduction apparatus can output reproduced data continuously.
In addition, Japanese Published Patent Application No.Hei.9-17124 discloses another shockproof function utilizing subcode data. When the buffering is interrupted, the shockproof function disclosed herein reads out and holds time information contained in subcode data which is written last, returns a CD pickup unit to an interruption point, then compares time information of subcode data included in data read out thereat with the time information held at the interruption, and instructs a timing of the buffering resumption.
On the other hand, when data is read out by the optical disk reproduction apparatus, errors may creep in the data. Further, there is a possibility that errors still remain in data after error correction is performed and that the data containing the errors are output as reproduced data. Here, in many cases, the errors contained in the reproduced data are of a negligible level. Particularly, in case of a musical CD where adjacent data have high correlations, even if a few errors are contained in the reproduced data, the errors cannot be recognized by the human ear in many cases.
In the prior art optical disk reproduction apparatus as described above, errors occurring also during a usual reproduction, independent of the buffering interruption, may be contained in the expectation data held in the comparator 255 and the CD-DA data. Therefore, in some cases, the comparator 255 cannot confirm coincidence of all data sequences and thus, the buffering cannot be resumed.
The present invention is made to solve the above problems, and it is an object of the present invention to provide an optical disk reproduction apparatus which can appropriately instruct buffering resumption, even when errors occurring in data independent of the buffering interruption are contained.
In addition, in the method disclosed in Japanese Published Patent Application No.Hei.9-17124, since the CD-DA data is not buffered by directly utilizing the time information of subcode data, a timing of the buffering and a timing of reading subcode data do not always completely coincide. Therefore, when the buffering is resumed on the basis of the confirmation of only the subcode data, it may occur that discontinuous data are buffered.
The present invention is made to solve the above problems, and it is an object of the present invention to provide an optical disk reproduction apparatus and a controlling method therefor, which apparatus can appropriately instructs the buffering resumption without utilizing the subcode data.
The present invention provides an optical disk reproduction apparatus which receives a reflected light obtained by irradiating a laser light to an optical disk thereby reading data recorded on the optical disk, temporarily buffers the data in a successively rewritable memory having a prescribed capacity, and then outputs the data as reproduced data, and comprises control means for resuming reading the data from the optical disk when buffering to the memory is interrupted, data coincidence detecting means for dividing first data buffered in the memory before the buffering interruption and second data read out by the control means into xe2x80x9cnxe2x80x9d groups, respectively, and detecting whether the first data and the second data are in coincidence for each group, and a buffering resumption request generating circuit for instructing a timing of buffering resumption on the basis of a result of the data coincidence detecting means.
Further, in the present invention, the data coincidence detecting means further comprises plural comparators each of which holds the first data and the second data, which are divided into the plural groups, one group by one, and compares the both data to decide whether each group of the divided data are in coincidence, an adder for obtaining a total number of the groups, for which groups it is decided that the first data and the second data are in coincidence, and a subtracter for obtaining a value of (a prescribed decision threshold)xe2x88x92(the total number)/(the value of xe2x80x9cnxe2x80x9d), and the buffering resumption request generating circuit instructs the timing of buffering resumption when the value obtained by the subtracter is 0 or less.
Further, in the present invention, the decision threshold can be set manually.
Further, in the present invention, the decision threshold is a ratio of an amount of data which is correctly reproduced to an amount of data which is reproduced by the optical disk reproduction apparatus.
Further, the present invention provides a control method for controlling an optical disk reproduction apparatus which receives a reflected light obtained by irradiating a laser light to an optical disk thereby reading data recorded on the optical disk, temporarily buffers the data in a successively rewritable memory having a prescribed capacity, and then outputs the data as reproduced data, and comprises a control step for resuming reading the data from the optical disk when buffering to the memory is interrupted, a data coincidence detecting step for dividing first data buffered in the memory before the buffering interruption and second data read out in the control step into xe2x80x9cnxe2x80x9d groups, respectively, and detecting whether the first data and the second data are in coincidence for each group, and a buffering resumption request step for instructing a timing of buffering resumption, on the basis of a result of the data coincidence detecting step.
Further, the present invention provides a storage medium storing a program code for executing the optical disk reproduction apparatus control method.
Further, in the present invention, the data coincidence detecting step further comprises a comparison step for holding the first data and the second data, which are divided into the plural groups, one group by one, and comparing the both data thereby deciding whether the data are in coincidence, an addition step for obtaining a total number of the groups, for which groups it is decided that the first data and the second data are in coincidence, and a subtraction step for obtaining a value of (a prescribed decision threshold)xe2x88x92(the total number)/(the value of xe2x80x9cnxe2x80x9d), and the buffering resumption request step instructs the timing of buffering resumption when the value obtained in the subtraction step is 0 or less.
Further, the present invention provides a storage medium storing a program code for executing the optical disk reproduction apparatus control method.
According to the present invention, when the buffering to a memory is interrupted for some reason, the optical disk reproduction apparatus can resume the reading of data from the optical disk, divide each of the first data buffered in the memory before the buffering interruption and the second data read out after the buffering interruption into plural groups, and detect whether the first data and the second data are in coincidence for each group, and instruct the timing of buffering resumption on the basis of that result. Therefore, even if an error occurring also at normal reproduction, independent of the buffering interruption, is contained in data to be compared, the buffering resumption can be instructed appropriately.
In addition, according to the present invention, the optical disk reproduction apparatus instructs the timing of buffering resumption by utilizing the CD-DA data. Therefore, the timing of buffering can be instructed more correctly, with relative to an optical disk reproduction apparatus and a control method therefor, in which the timing of the buffering resumption is instructed by utilizing only the subcode data.